The alarm bells are going off across the City

Between sleeping and waking, there is a middle phase: you realise it’s time to get up, but can’t quite bear to admit you need to get out of bed. London’s debt capital markets teams are in that zone. Brexit’s alarm has sounded, but few are eager to haul themselves into the cold air of Frankfurt or Paris.

Until the sleepers get up, the plans going through their heads are invisible; they all look like they are still in bed. Thus, hardly any bankers have actually left London for the EU 27 yet. Very soon, the picture will be sharply different.

The legal issues involved are complex, with a huge range of interpretations that vary between national regulators, banks and products. But it is no longer possible to ignore the underlying logic.

Capital markets are regulated, and EU capital markets are regulated as one. Many services will have to be provided by EU-regulated entities and people. Regulators might allow some people to spend much or most of their time in the UK, but they have little incentive to be generous. Barring an 11th hour escape from Brexit, slowly but surely, jobs that face EU clients — which is most of them — will be winched across the Channel.

What is achieved by March 29 will be the absolute essential — more will follow. Banks are not rushing because it disrupts staff. But gradually, colleagues will tell each other Paris, Frankfurt and Amsterdam are not so bad and the resistance will lessen. Paris has an edge because of the Eurostar.

Banks and bankers will be fine. It is London and the UK that are about to suffer an nightmare that they will struggle to wake up from.